1. Field of the Invention
This invention relates to compact disk players' and is more particularly concerned with compact disk players provided with a peak search facility or function for use, for example, in the dubbing of data from a compact disk to another recording device.
2. Description of the Prior Art
Compact disk (CD) players, which can reproduce data (for example audio data) recorded on compact disks, are of course well known. It has been proposed that a CD player be capable of conducting a peak search. That is, the player is provided with means for detecting a peak signal level. The detected peak level may, for example, be used to facilitate setting of a recording level when dubbing from a compact disk to a tape recorder or the like is performed. More specifically, in the peak search mode, track jumps are repeatedly carried out, for example over every 10 tracks, and an audio signal is reproduced for each of the track jumps for a predetermined time interval. Every time an audio signal is reproduced, the peak level thereof is detected. Thus, the position of the track where the signal with the largest sound volume or level is recorded is approximately detected.
The above-described previously proposed CD player demodulates and temporarily stores regenerated (picked up) signals in a memory circuit, and the CD player then outputs the signals after subjecting them to error correction.
For this reason, as shown in FIG. 1 of the accompanying drawings, audio signals S.sub.OUT (FIG. 1(B)) are outputted by the CD player until a time t.sub.1, when all the regenerated signals which have been stored in the memory circuit are outputted, even if the level of a track jump signal S.sub.J (FIG. 1(A)) rises at a time t.sub.0 to start a track jump. After the time t.sub.1, regenerated signals obtained during the track jump are processed and then outputted.
Accordingly, during a time interval T.sub.1 immediately after the track jump, resetting of a peak level detection circuit (not shown) for detecting the peak level initiate detection of the peak level of pretrack jump audio signals S.sub.OUT being started.
Stable tracking control is not possible immediately after the track jump and thus the occurrence of errors cannot be avoided. For this reason, post-track jump audio signals S.sub.OUT are outputted after the elapsing of a time interval T.sub.2 starting at the time t.sub.1, the time interval T.sub.2 being longer than the time interval (duration) T.sub.J of the actual track jump.
During the time interval T.sub.2, the signal level of the audio signals S.sub.OUT is held according to the result of the error detection. Thus, the signal level at the time t.sub.1 is held.
Thus, when a reset signal RST (FIG. 1(C)) is supplied to the peak level detection circuit during the time interval T.sub.2, this initiates in detection of the peak level of the pre-track jump audio signals S.sub.OUT .
Accordingly, until a time t.sub.3 at which tracking control becomes stable after the track jump, and when post-track jump audio signals S.sub.OUT are outputted, it is not possible to start correct detection of the peak level of the audio signals S.sub.OUT.
Thus, in a peak search operation, as shown in FIG. 2 of the accompanying drawings, in which peak level detection is performed twice for each track jump and in which an average value of the detection results is detected, an erroneous peak search result can be obtained.
More specifically, after a detection result of the peak level detection circuit is read, the peak level detection circuit is reset by raising the level of the reset signal RST (FIG. 2(A)), and then a track jump is carried out by raising the level of (pulsing) the track jump signal S.sub.J (FIG. 2(B)).
Furthermore, after the track jump signal S.sub.J rises, the detection result of the peak level detection circuit is received after a predetermined time interval T.sub.4, and the reset signal RST rises again.
In a case where an average value is obtained by reading in peak level detection results twice for every track jump in this manner, during a time interval between a time t.sub.5 and a time t.sub.6 (FIG. 2(C)), at which times the reset signal RST is pulsed again, the pre-held peak level can be higher than a post-track jump peak level and hence the pre-track jump peak level L.sub.2A is detected. On the other hand during the time interval between the time t.sub.6 and a time t.sub.7, a peak level L.sub.2B is detected.
Acoordingly, during the time interval between the time t.sub.5 and the time t.sub.7, the peak level of a first recording track A is detected, but an average value of the peak levels L.sub.2A and L.sub.2B is detected. Thus, this results in an erroneous detection result.
On the contrary, during the time interval between the time t.sub.7 and a time t.sub.8, the pre-held level is lower than the post-track jump peak level, and hence a post-track jump peak level L.sub.3A is detected. On the other hand, during the time interval between the time t.sub.8 and a time t.sub.9, a post-track jump peak level L.sub.3B is detected.
Thus, during the time interval between the time t.sub.7 and the time t.sub.9, the peak level of a second recording track B is correctly detected.
For these reasons, the previously proposed CD player involves a problem in that although a post-track jump peak level can be correctly detected, a pre-track jump peak level can be erroneously detected.
To solve this problem, detection of a peak level could be started immediately after the time t.sub.3 after which post-track jump audio signals S.sub.OUT are outputted. That is, after a peak level detection result is read at the time t.sub.3, the reset signal RST would be caused to rise.
However, it is unavoidable that the time interval T.sub.3, namely the interval from the time t.sub.0 of the start of the track jump to the time t.sub.3 of outputting the post-track jump audio signals S.sub.OUT (FIG. 1), changes according to the track jump amount, characteristics of the tracking control circuit, the timing of the start of the track jump and, other factors.
To obtain, in practice, a correct peak search result, it is not possible to output a reset signal RST until a sufficient time interval has elapsed after the track jump signal S.sub.J has returned to its low level to terminate the track jump. This raises a problem of a considerable time of time being required for carrying out the peak search.
An object of the invention is to provide a CD player which overcomes the disadvantages set out above.
Another object of the invention is to provide a CD player which can accurately and swiftly detect peak levels on a compact disk.
A further object of the invention is to provide a CD player which is capable of reducing the time necessary for carrying out a peak search by effectively avoiding errors in the peak search.